The cell cycle is the process by which a cell grows, replicates its DNA, and divides into two daughter cells. It is divided into two main phases: interphase and the mitotic phase.
Interphase:
- Interphase is the longest phase of the cell cycle, accounting for about 90% of the total cycle time.
- During interphase, the cell grows and replicates its DNA in preparation for cell division.
- Interphase is divided into three stages: G1 (gap 1), S (synthesis), and G2 (gap 2).
- During G1, the cell grows and prepares for DNA replication.
- During S, DNA replication occurs, resulting in two identical copies of each chromosome.
- During G2, the cell continues to grow and prepares for mitosis.
Mitotic phase:
- The mitotic phase is the shorter of the two phases and consists of mitosis (nuclear division) and cytokinesis (cytoplasmic division).
- Mitosis is divided into four stages: prophase, metaphase, anaphase, and telophase.
- During prophase, the chromatin condenses into visible chromosomes, the nuclear envelope breaks down, and the mitotic spindle begins to form.
- During metaphase, the chromosomes align along the equator of the spindle (the metaphase plate).
- During anaphase, the sister chromatids separate and move to opposite poles of the spindle.
- During telophase, the chromosomes begin to decondense, the nuclear envelope reforms, and the spindle begins to disassemble.
- Cytokinesis occurs after mitosis and involves the physical separation of the two daughter cells.
Overall, the cell cycle and mitosis are critical processes that ensure the accurate transmission of genetic information from one generation of cells to the next. These processes are tightly regulated and involve a complex interplay of signaling pathways, enzymes, and structural proteins.